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351.
Md. Naziruddin Khan A. S. AI-Dwayyan Z. H. Zaidi 《中国物理快报》2006,23(9):2407-2410
Chrysene and 1.2-benzanthracene are successfully doped in a solid wax film and their vibrational spectra in gooo--400cm^-1 are discussed. The harmonic frequencies and relative intensities of both the molecules observed in the film are compared with theoretical values calculated by the density functional theory (DFT) model as well as with the previous experimental data. The effects on spectra due to change of matrix and some additional bands observed in the wax film are also reported. Excellent agreement in the spectral positions and strengths between the experiments and DFT values are found. 相似文献
352.
Solutions are presented for the impulsively started uniformstream and simple shear flows past a point source of momentum,which can be interpreted to describe the position and the widthof the front which transmits the knowledge of the singularitythrough a slightly viscous fluid. These understandings are thengeneralized to show that the front always moves with velocityslower than that of a (strictly monotonic) convective velocity,and also that its width always grows faster than with simplediffusion. Finally, a remarkably simple, exact expression is given forvorticity due to a simple shear flow past a point vortex. 相似文献
353.
S. Trebert Haeberlin F. Lux J. Karl T. Spruss H. Schönenberger 《Journal of Radioanalytical and Nuclear Chemistry》1987,113(2):461-467
As part of an examination of the cytostatic effects of 1,2-diarylethylenediamine-platinum(II)-complexes the contents of platinum and biologically essential trace elements of tumour tissue and different organs were determined. The activation analysis procedure — separation of32P, isolation of199Au and99Mo — is described. In the course of a pharmakokinetical experiment with tumourbearing rats (DMBA induced hormone-dependent tumours) the desired enrichment of the administered drug in the tumour tissue was found. Changes of the trace element level of tumour tissue were found for hormone-dependent MXT-mammary tumours on mice. 相似文献
354.
J. Xu J. Mei X.H. Huang X. Li Z. Li W. Li K. Chen 《Applied Physics A: Materials Science & Processing》2005,80(1):123-126
The effect of nitrogen surface doping on the electron field emission characteristics of hydrogenated amorphous carbon films was studied. It was found that the emission threshold electric field decreased after nitrogen surface doping which indicated the reduction of the emission barrier at the film surface. It was demonstrated that this improvement arose from the decrease of the effective work function due to the formation of a dipole layer induced by chemical termination and chemical structural change on the film surface. PACS 52.75.Xx; 73.30 +y; 73.61.Jc 相似文献
355.
Q. Gong R. N tzel P.J. van Veldhoven T.J. Eijkemans J.H. Wolter 《Journal of Crystal Growth》2005,280(3-4):413-418
We report on the shape transition from InAs quantum dashes to quantum dots (QDs) on lattice-matched GaInAsP on InP(3 1 1)A substrates. InAs quantum dashes develop during chemical-beam epitaxy of 3.2 monolayers InAs, which transform into round InAs QDs by introducing a growth interruption without arsenic flux after InAs deposition. The shape transition is solely attributed to surface properties, i.e., increase of the surface energy and symmetry under arsenic deficient conditions. The round QD shape is maintained during subsequent GaInAsP overgrowth because the reversed shape transition from dot to dash is kinetically hindered by the decreased ad-atom diffusion under arsenic flux. 相似文献
356.
Theresa J. Hermel-Davidock H. Sean Tang Daniel J. Murray Stephen F. Hahn 《Journal of polymer science. Part A, Polymer chemistry》2007,45(24):3338-3348
It has been found that by the addition of low concentrations of an amphiphilic block copolymer to an epoxy resin, novel disordered morphologies can be formed and preserved through curing. This article will focus on characterizing the influence of the block copolymer and casting solvent on the templated morphology achieved in the thermoset sample. The ultimate goal of this work is to determine the parameters that would control the microphase morphology produced. Epoxy resins blended with a series of amphiphilic block copolymers based on hydrogenated polyisoprene (polyethylene-alt-propylene or PEP) and polyethylene oxide (PEO), specifically, were investigated. In this article, the cure-induced order–order phase transition from the spherical to wormlike micelle morphology will also be discussed. It is proposed that the formation of the wormlike micelle structure from the spherical micelle structure is similar to the phase transition behavior that occurs in dilute block copolymer solutions as a function of the influence of the solvent on micelle morphology. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3338–3348, 2007 相似文献
357.
Q.-Y. Shao A.-D. Li J.-B. Cheng H.-Q. Ling D. Wu Z.-G. Liu N.-B. Ming C. Wang H.-W. Zhou B.-Y. Nguyen 《Applied Physics A: Materials Science & Processing》2005,81(6):1181-1185
LaAlO3 (LAO) gate dielectric films were deposited on Si substrates by low-pressure metalorganic chemical vapor deposition. The interfacial structure and composition distribution were investigated by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectroscopy (SIMS), and Auger-electron spectroscopy (AES). HRTEM confirms that there exists an interfacial layer between LAO and Si in most samples. AES, SIMS, and XPS analyses indicate that the interfacial layer is compositionally graded La–Al silicate and the Al element is severely deficient close to the Si surface. Electrical properties of LAO films were evaluated. No evident difference in electrical properties between samples with and without native SiO2 layers was observed. The electrical properties are discussed in terms of LAO growth mechanisms, in relation to the interfacial structure. PACS 73.40.Qv; 81.15.Gh; 77.55.+f; 68.35.-p 相似文献
358.
The effect of hydrostatic pressure on the structure of a plastic columnar discotic triphenylene has been investigated. The goal was to determine whether pressure can be used to modify electronic properties via changes in structural properties of columnar discotics to any significant extent. The findings are that (i) the intra- and inter-columnar distances are reduced in a nearly isotropic fashion, (ii) that the crystal sizes are reduced and (iii) that a transition takes place from a more highly ordered plastic columnar to a less ordered hexagonal columnar state with increasing pressure. The induced decrease of the molecular distances, amounting to 6% for pressures up to 17 kbar, are clearly too small to induce an appreciable modification of the electronic structure and thus opto-electronic properties. 相似文献
359.
Vlasov Yu. G. Murzina Yu. G. Legin A. V. Ermolenko Yu. E. Schubert J. Schüoning M. J. Lut H. 《Russian Journal of Applied Chemistry》2002,75(3):351-356
Methods of silicon planar technology and pulsed laser deposition were applied to fabricate fully solid-state chemical sensors for determining ions of copper, lead, cadmium, thallium, and also sulfide and chloride ions on the basis of thin chalcogenide films as ion-sensitive membranes. 相似文献
360.
N. H. Abu-Hamdeh 《Heat and Mass Transfer》2002,38(7-8):687-693
The analytical solutions of equations describing the dynamics of distributed parameter systems are usually complicated in
form and derivations and inconvenient to use for simulation and control system design. The liquid–liquid counter flow heat
exchanger is an example of these disturbed parameter systems. An analytical solution of the dynamics of a symmetrically operated
counter flow heat exchanger in the form of transfer function matrix is investigated in open-loop and close-loop conditions.
The resulting non-linear model was linearized using perturbation approach. A feed-forward path controller to counteract at
any disturbances in the boundary temperature and a non-interactive controller to decouple the outputs were implemented.
Received on 22 February 2001 / Published online: 29 November 2001 相似文献